I tripped while carrying my son up the steps in our building today and he got a very strong hard knock on his forehead, just above his eye. He now has a very swollen, scary looking protrusion and has also had bad diarrhea since then. Is that a reason for concern?

Any serious head bump + any new symptoms at all would = trip to ER if necessary but immediate discussion with doctor at any rate. If you go to a pediatric group that has an on-call doctor, that would work, but I'd have him looked at a doctor pretty immediately. We aren't doctors here and head injuries can be really serious.